In manufacturing operations, complicated assemblies and contoured parts are often mated to other complicated assemblies and parts. A variety of techniques are currently used to locate the assemblies and parts for mating.
For example, some assembly techniques use factory aids such as templates that are made out of paper, Mylar™, or the like to find reference targets for accurately placing smaller parts on larger parts. These factory aids are subject to wear and tear and, as a result, are replaced from time-to-time. The factory aids must be replaced when engineering changes are made. Also, errors may be made by manufacturing personnel when using the factory aids. All of these aspects of the factory aids introduce additional costs into the manufacturing operation.
In other assembly techniques, a laser tracker measures coordinates of a number of reference targets of known design points on a large part. In this case, the large part is assumed to have been built identically to a defined design. This technique allows the laser tracker to “buck” into the part's coordinate system, or to locate precisely the coordinate system of the tracker with respect to the coordinate system of the part. When a smaller part is to be mounted onto a larger part, a laser tracker with a visible beam points onto the larger part and can thus designate the mounting position to guide the mechanic in the assembly.
However, this technique only gives one point indicating the location of the part. Typical laser trackers are not able to directly measure the coordinates of the mounted hardware relative to the reference targets or other mounted hardware. This is because typical laser trackers only measure off retro-reflective targets, and because the line-of-sight path between the laser and the retro-reflective targets is blocked.
Use of retro-reflective targets introduces additional time and labor costs into manufacturing operations. Most retro-reflectors must be positioned within a small range of angles to be useful, so time and effort are expended setting up the targets. Further, the retro-reflectors must be periodically pointed and re-pointed to remain within the useful range of angles. Because of their angle-sensitivity and time requirements, retro-reflectors are not able to be used to make measurements in a production line as part of the production process. Instead, retro-reflectors are typically set up and measurements are typically performed on back shifts, such as a midnight shift, when production operations are not being performed.
Further, laser trackers cannot provide the factory aid function described above, such as would provide information about how the part should be oriented. If information regarding orientation of the part is desired, then the desired orientation information is currently provided by a different system using a different laser that passes through a laser galvanometer scanner that is positioned next to the laser tracker. The scanner motor and mirrors are much more agile than those of the laser tracker, such that a pattern may be drawn at an update rate that appears to be a projected pattern.
To project the pattern, the projector needs to know the part definition and the position of the tool and/or workpiece onto which it projects the pattern. The laser radar allows the projector to acquire the position of the tool and/or workpiece. Because known systems use a separate tracker and a separate projector, the relative positions of the tracker and the projector need to be known and resolved, especially when operating at tolerances on the order of 1/1000 inch or less for critical operations.
It would be desirable to perform measurements without retro-reflectors and project information using a single system. However, there is an unmet need in the art for a system and method for performing measurements without retro-reflectors and for projecting information with the same system.